Recombinant Cholera Toxin B subunit [FITC]

Cholera toxin is a potent enterotoxin from Vibrio cholerae with specific structural and functional features. It consists of an A subunit (CTA) and five B subunits (CTB), making it a molecular meshwork. The CTA is the toxic unit, while CTB is the non-toxic receptor-binding unit capable of attaching to GM1 receptors on cell membranes. This binding allows antigens linked to the B subunit to maintain prolonged contact with immune cells, inducing oral tolerance to ingested antigens. CT is extremely toxic, with as little as 8μg capable of causing severe diarrhea. However, it simultaneously exhibits strong immunogenicity, making it an important mucosal immune adjuvant.

Figure 1. Structure of cholera toxin
(Source: Day CA, et al. 2015)

Despite CT's potent immunogenicity and adjuvant effects, its high toxicity precludes direct human application. To address this issue, researchers have developed various improvement strategies. The primary approach involves using genetic engineering to modify the A subunit or utilizing the CTB alone as an adjuvant. As a non-toxic mucosal carrier molecule, CTB shows promising applications in vaccine development and immunotherapy. It can form new antigen complexes with other antigens through chemical conjugation or genetic fusion. This method not only induces oral tolerance but also significantly reduces the required antigen dose. In practical applications, CTB has been proven to effectively enhance immune responses, particularly in inducing mucosal immunity and oral tolerance. For instance, in peanut allergy research, mixtures of CTB and peanut antigens significantly increased levels of specific immunoregulatory cells and cytokines, offering new insights into allergy treatment. Overall, while CT itself cannot be directly applied to humans due to toxicity issues, its B subunit CTB has become an important tool in vaccine development and immunotherapy, especially in inducing mucosal immunity and oral tolerance. As research progresses, CTB's potential applications in immunology are expected to expand further.

Beyond its applications in vaccines and immunomodulation, CTB demonstrates potential in other areas. In certain autoimmune disease models, CTB exhibits anti-inflammatory properties. Its potential to induce oral tolerance, suppress allergies, and mitigate autoimmune diseases has attracted researchers' attention. Additionally, CTB serves as a research tool, such as a neuronal tracer for mapping neural pathways and for identifying lipid raft structures on cell surfaces.

Recombinant CTB subunit [FITC]